Solvent and Substituents Effect on the UV/Vis Absorption Spectra of Novel Acidochromic 2-Aminothiazole Based Disperse Mono Azo Dyes

Abstract

The effect of solvent atmosphere on the electronic absorption properties of 2-aminothiazole based monoazo disperse dyes are studied. The synthesized monoazo dyes with different substituents on the para position of phenyl ring led to changes in the absorption properties of these dyes. Further, the positive solvatochromism data was evaluated to get the excited and ground state dipole moment ratio of the dyes. The Kamlet-Taft and Catalan polarity scales were employed wherein the solvent basicity and dipolarity is responsible for the bathochromic shift with increase in solvent polarity. The free amino group in the dyes made it responsive towards protonation by trifluoroacetic acid. The acidochromic behavior of the dyes was studied and D1, D3, and D4 exhibited major color change to longer wavelength with emergence of a new red shifted absorption band at 556 nm, 580 nm, and 540 nm, respectively, in their absorption spectra. Thus with help of simple UV-Vis absorption studies, we have studied the intermolecular interactions of the 2-aminothiazole based mono azo acidochromic probe.